The invention concerns a film for the manufacture of self-adhesive, especially label film laminates that may be stamped, a process for its manufacture as well as its use.
Multilayered label films are known (U.S. Pat. No. 6,042,907), which comprise two unfoamed layers and essentially consist of polyolefin, polystyrene or styrene-butadiene-styrene-blockcopolymers as a compatibility agent. The known label film is structured in two layers, it can however carry additional layers that have certain functions. Such label films are characterized as xe2x80x9cblend filmsxe2x80x9d (Engl. blend=Mischung) The special characteristic of polyolefin, namely abrasion resistance and hardness in combination with rigidness and machine-processability, can in this way be combined as the outstanding characteristics of polystyrene.
Experiments have shown that a blend of polyolefins and polystyrene as a layer delivers results for the purpose of the U.S. patent, however these results have to be improved, especially with regard to the production. Furthermore, the known blend films have the disadvantage that the blends always lead to cloudy films, since polyolefin-polystyrene blends do not provide a homogenous crystalline structure.
The task of the invention at hand was to provide an improved label film. The improved film should be able to be manufactured cost-efficiently. It should be easy to cut and perforate and also be superior to the known film with regard to its elastic capability and its puncture resistance. It should also possess a high level of transparency and glossiness and a high usage value. Finally, the printability of the film must also be guaranteed.
This task was able to be solved in that, for a film of the type mentioned at the beginning, consisting of at least three layers, the inner layer consists of polyolefins and/or olefin-copolymers and for which the layers present on both sides of the inner layer consist of a blend of styrene-butadiene-styrene-blockcopolymers and polystrene-homopolymers. A mixing or making compatibile of polyolefins and polystyrene does not occur.
Other known self-adhesive laminates are used for the labeling and ticketing of products. These laminates are composed of a base material, pressure sensitive adhesive and a cover film (usually of siliconized paper or plastic material). In addition to paper, polyolefin film also serves as base material. For example, polyethylene film in thicknesses between 70 and 150 xcexcm and biaxial oriented polyprophlen-films in a thickness between 50 to 60 xcexcm are used. The latter have a high specific bending resistance, which makes them useable even for these small thicknesses.
It has however been determined that films oriented in such a way have a very small elastic capability and malleability, which is necessary for the labeling of embossed surfaces and for containers that are deformed after being filled.
A laminated labeling film for the labeling in the blow mold is known from DE 198 59790 A1. The films of the type here claimed in claim 1 differ from this. With the known laminated label films, for example, a multi-layered inner ply is mentioned that is laminated onto a polyolefin stiffening ply, whereby the inner ply can also be multilayered. It can comprise of a core layer and an outer seal layer of polystyrene. This polystyrene layer should be able to be sealed to a plastic container at 600xc2x0 C. to 100xc2x0 C. For the film at hand, comparable layers are not manufactured from polystyrene, but rather of a mix of SBS-blockcopolymers and polystyrene-homopolymers. This is also not an IML-film.
Therefore, in the task mentioned above, the known films should be improved with regard to elastic capability and malleability. Even this requirement is mastered by the new film system mentioned, polystyrene-polyolefin-polystyrene.